puppeteer/website/versioned_docs/version-21.3.4/api/puppeteer.eventemitter.on.md

---
sidebar_label: EventEmitter.on
---

# EventEmitter.on() method

Bind an event listener to fire when an event occurs.

#### Signature:

```typescript
class EventEmitter {
  on<Key extends keyof EventsWithWildcard<Events>>(
    type: Key,
    handler: Handler<EventsWithWildcard<Events>[Key]>
  ): this;
}
```

## Parameters

| Parameter | Type                                                                                                                  | Description                                                        |
| --------- | --------------------------------------------------------------------------------------------------------------------- | ------------------------------------------------------------------ |
| type      | Key                                                                                                                   | the event type you'd like to listen to. Can be a string or symbol. |
| handler   | [Handler](./puppeteer.handler.md)&lt;[EventsWithWildcard](./puppeteer.eventswithwildcard.md)&lt;Events&gt;\[Key\]&gt; | the function to be called when the event occurs.                   |

**Returns:**

this

`this` to enable you to chain method calls.